THURSDAY, Oct. 11 (HealthDay News) -- The latest attempt to fight the mental ravages of Alzheimer's disease involves an international study of three different drugs in people destined to develop the brain disorder.

The large trial, scheduled to start next year, will assess the drugs' success in a group of people with gene mutations that practically guarantee they'll get Alzheimer's, but who do not yet have symptoms.

There is no cure for the condition, which gradually robs people of their memory and their ability to live their everyday lives.

The 160 American, Australian and British volunteers will likely start showing declines in memory and thinking within five years unless the drugs work, The New York Times reported.

The three drugs selected for the study were among 15 submitted by pharmaceutical companies. The final choices were based on the best evidence of effectiveness and lowest risk of dangerous side effects, The Times reported.

The drugs chosen are Roche's gantenerumab and two drugs made by Eli Lilly and Co., one called LY2886721 and the other called solanezumab, according to the news report.

The drugs use different approaches to target beta amyloid, a protein that forms the brain plaques characteristic of Alzheimer's.

"These trials will be the best test of the amyloid hypothesis ever undertaken," said Dr. Sam Gandy, associate director of the Mount Sinai Alzheimer's Disease Research Center in New York City.

"The drugs that they chose were the best options at the moment," he said.

One of the Lily drugs, called a BACE inhibitor, thwarts the beta-secretase enzyme involved in amyloid production. "If the BACE inhibitor succeeds, the immediate impact will be greater because that is given orally while the others are infusions," Gandy explained.

But even if one or all of the drugs works, cost will limit speedy access worldwide, Gandy added.

The Alzheimer's Association, which provided significant financial backing for the trial, said Thursday it was a groundbreaking effort.

"The Alzheimer's Association has put in $4.2 million because we feel this is testing a very important class of drugs in a special population that may give us an answer to how the disease begins," said Dean Hartley, director of scientific initiatives at the association. "We are trying to find these mechanisms, and how they progress through the disease process."

This study, and other Alzheimer's prevention trials that are starting soon, are very important for both the Alzheimer's research community and for people with Alzheimer's and their families, Hartley added, because better treatments and prevention strategies are needed for the millions who are now living with Alzheimer's.

Other drugs and treatment strategies must still be tested, Hartley said, and drugs need to be developed for people with late-onset Alzheimer's dementia who are already experiencing symptoms.

The latest study represents a shift in thinking about Alzheimer's research. After repeated failed attempts to treat people who already have the degenerative disorder, researchers said studies need to be conducted in people who do not yet have the disease. Proponents argue that the time to tackle Alzheimer's is before the brain is irreversibly damaged.

In related news, another study starting next year will look at an extended family in Colombia that shares a gene mutation that causes Alzheimer's. In a third study, researchers will look at people in the United States aged 70 and older who have no known gene mutations linked to Alzheimer's but have signs of the disease on brain scans, The Times reported.

More than 5 million Americans have Alzheimer's disease, and that number is expected to soar as the Baby Boom generation ages. It is estimated that the cost of caring for Alzheimer's patients in the United States will reach $200 billion in 2012, according to the Alzheimer's Association.